Tool manufacturing method

ABSTRACT

A method for manufacturing hand tools, such as wrenches. The method generally includes the steps of providing a flat stock, cutting the flat stock into the desired two-dimension blank using a laser, and three-dimensionally machining the laser-cut 2D blank into the desired three-dimensional workpiece. The tool may undergo a heating treatment process and a surface treatment process. In the context of a wrench, the blank may be laser cut with a laser beam oriented to cut generally perpendicularly to the plane of the flat stock. After laser cutting, the handle and interface region between the handle and jaw(s) are machined to provide the desired three-dimensional shape. For example, the three-dimensional shape may be selected to provide a comfortable grip even when applying a high level of force. The wrench jaw may have an optimized geometry calculated so that there is no excess material or “over-designed” regions of the jaw. The wrench jaw has internal corners with optimized radii.

BACKGROUND OF THE INVENTION

The present invention relates to tools, such as wrenches, and moreparticularly to methods for manufacturing tools.

It is a long-held and well-accepted belief that certain hand tools mustbe made using a forging process. For example, it is universally believedthat wrenches of adequate function and strength must be manufacturedthrough forging. Conventional wisdom is that forging is required to forma strong, high quality, general purpose wrench, such as a mechanic mightuse day to day. This belief has long been held not only by users ofwrenches, but also by manufacturers of wrenches and, despiteadvancements in manufacturing technologies, this belief continues to beheld to this day.

Forging can be done using a forging press or forging hammer. FIG. 1shows a conventional forged combination wrench manufactured inaccordance with the prior art. The forged wrench of FIG. 1 is typicallymanufactured from a bar stock, such as the cylindrical bar stock of FIG.2. The bar stock is hammered into the desired shape. The press or hammerrequires expensive tools and dies which are unique to a single part.Much of the reason that wrenches are forged is due to conventionalthinking and practices. Hand tools have been forged for thousands ofyears. Forging is also often thought to create a tougher part that isstronger and/or more ductile due to grain flow during deformation of thepart. It can sometimes achieve a near finished shape from a singleprocess. A forging process can be economical at very high volumes, whenthe cost of tooling is offset. A forged wrench will generally requiresecondary machining operations or broaching to achieve proper openingsand precise geometry. To illustrate, most wrench openings are cut toprecise tolerances using a broaching machine. Like forging, broachingrequires expensive custom tooling for each size desired.

Although forging and broaching can be economical processes at very highvolumes, there is a long-felt and unmet need for an alternative processthat can achieve similar or higher strength, durability, andfunctionality at a competitive cost, without high initial investmentcosts for tooling, and while maintaining flexibility to iterate designs.At lower volumes, forge and broach tooling costs can take many years oreven decades to offset.

Forging suffers from other disadvantages. For example, there aremeaningful practical limitations on the shapes that can be formed usingconventional forging processes. For the case of wrenches and other handtools, the metal generally starts as a straight, cylindrical billet.Shapes created in a forging process are limited to how far the mold canstretch or smash the metal. For example, the capital letter “T” would bevery difficult to forge because it would require the straight billet tobe stretched dramatically at one end perpendicular from its axis. Whenlaser cut from a plate of steel, however, a capital “T” would be verysimple to form. This difference is relevant to wrenches with forms thatdeviate from a straight handle axis. For example, some wrenches(including a style called “angle wrenches”) can work best with largeangular and locational jaw offsets relative to the handle when comparedto other common wrenches (such as combination wrenches). This shapewould require the steel billet material to stretch more. This increasedstretch could require higher forge temperatures, higher press forces, ormulti-stage molds. These in turn could increase tool wear or even makethe geometry impossible to reasonably form. While there are options tobend the steel before or after forging (for example, if you were toforge an “S” shape, you could first bend the billet in two locations toform a backward “Z” shape; the “Z” billet would then be forged to forman “S”), these options still do not easily form shapes like the letter“T”

SUMMARY OF THE INVENTION

The present invention provides a method for manufacturing hand tools. Itis particularly well-suited for manufacturing wrenches and, moreparticularly, for angle-head wrenches. The method generally includes thesteps of providing a flat stock, such as a sheet stock or a plate stock,cutting the flat stock into the desired two-dimensional blank using alaser, and three-dimensional machining the laser-cut blank into thedesired three-dimensional form. The steps of machining and laser-cuttingmay be implemented in any order. Following the final forming operation,the tool may undergo surface treatment and heating treatment steps.

In one embodiment, the blank is laser cut with a laser beam oriented tocut generally perpendicularly to the plane of the flat stock to form awrench having at least one jaw extending from one end of a handle. Afterlaser cutting, the handle and interface region between the handle andjaw are machined to provide the desired three-dimensional shape. Forexample, the three-dimensional shape may be selected to provide acomfortable grip even when applying a high level of force. As anotherexample, the handle may be machined to round the corners and to providea generally oval cross-sectional shape, which not only provides comfort,but also gives the wrench a conventional aesthetic appearance.

In one embodiment, the workpiece may be bent, for example, to vary theangle of the jaw from the handle.

In one embodiment, the flatstock may be manufactured by providing ablock of steel and rolling the steel into a sheet or plate using arepetitive rolling process involving a series of sequential rollingoperations.

In one embodiment, the three-dimensional workpiece is subjected to anydesired surface treatment steps. For example, the surfaces of thethree-dimensional workpiece may be deburred/finished using conventionalfinishing methods such as, but not limited to, polishing, buffing,vibration polishing, electropolishing, shot blasting or shot peening.

In one embodiment, the three-dimensional workpiece is heat treated by aquench and temper process.

In one embodiment, the three-dimensional workpiece may be protected fromcorrosion by conventional protection methods such as, but not limitedto, electroplating, black oxide, galvanizing, or zinc phosphate.

In one embodiment, the present invention may be used to manufacture anangle-head wrench. In this embodiment, the wrench jaw has an optimizedgeometry calculated so that every cross section throughout the jaw beamwill reach the maximum stress, meaning that there is no excess materialor “over-designed” regions of the jaw. As a result, the wrench jaw hasthe slimmest possible geometry.

In one embodiment, the wrench jaw geometry is dictated by the followingequation:

${h(x)} = \sqrt{\frac{6F}{t\;\sigma}x}$

where F is the maximum force the wrench is designed to withstand, t isthe wrench thickness and σ is the allowable stress. For example, if thewrench jaw beam must withstand a 9,000 N force based on a 200 N*m torquespec, the jaw is 6 mm thick, and can reach 1,200 MPa before yielding,this equation shown below will generate the slimmest profile:

${h(x)} = {\sqrt{\frac{6*900{0\lbrack N\rbrack}}{{{6\left\lbrack {mm} \right\rbrack}*1},{20{0\left\lbrack {MPa} \right\rbrack}}}x} = \sqrt{{7.{5\left\lbrack {mm} \right\rbrack}}x}}$

In one embodiment, the wrench jaw has optimized internal radii. Morespecifically, the radii in the internal corners of the jaw opening aredesigned larger than competing wrenches. Sharp corners create stressconcentrations with higher stresses at the corner than at other parts ofthe cross section. Larger radii at a corner will reduce the stress inthe given corner. In the case of wrenches, a larger radius in the jawcorner will result in lower internal stress at the corner for a giventorque. In one embodiment, the radius in these angle wrenches is made aslarge as possible in order to reduce internal stresses and increasestrength. The size was constrained by hex contact. If the radius is toolarge, the flat portion of the wrench opening will decrease such thatthe flat surfaces of the hexagonal fastener will no longer be in fullcontact with the flats of the wrench opening. For these angle wrenches,the radius size, R, is about ⅓ the size of the wrench opening size, d,as in the equation shown below, where C₂ is a dimensionless constant.For this application, C₂ could range from about 2.5 to 3.8 whilemaintaining strength benefits of a large radius and still fitting ahexagonal fastener properly.

$R = {\frac{d}{C_{2}} = \frac{d}{3.1}}$

In one embodiment, the present invention provides an angle-head wrenchin which the centerline of the wrench jaw is significantly offset fromthe longitudinal centerline of the handle. The offset relationshipbetween the handle and the wrench jaw may make it easier to fit to nutsor bolts situated in tight confines. In one embodiment, the wrench jawis maximally offset or fully offset to enhance this feature to thegreatest possible degree. For example, the wrench jaw may be offset suchthat the outermost edge of the beam is substantially aligned orsubstantially flush with the corresponding edge of the handle. In atypical application of this feature, the wrench jaw and the handle maybe offset such that the longitudinal edge of the handle is essentiallytangent to the curved-outermost edge of the beam.

The present invention provides an improved process to make a wrench orother hand tool used to apply force to fasteners that provides at leastthe strength, durability, and functionality of traditional forgedwrenches, except using rolled steel (of various possible alloys) that iscut by a laser and machined to finish its form (regardless of order,whether laser cut first and then 3D machined, or 3D machined first andthen laser cut). The process allows for easy design changes/iterationsand is cost competitive to forging, but without expensive initialtooling costs. The absence of large tooling costs allows for quick andcheap design iteration and improvement. At very high volumes, theprocess can be automated with modular production cells, maintainingdesign freedom and competitive costs relative to forging. The presentinvention also allows the manufacture of tool shapes that would beexcessively expensive or difficult using conventional forgingtechniques. For example, the present invention is well-suited for use inmanufacturing angle-head wrenches, including angle-head wrenches inwhich the wrench jaw is both angled and offset from the centerline ofthe handle. As a result, the present invention can be used to producewrenches and other tools that are designed with shapes that areoptimized without being subject to the limitations of conventionalforging techniques.

These and other objects, advantages, and features of the invention willbe more fully understood and appreciated by reference to the descriptionof the current embodiment and the drawings.

Before the embodiments of the invention are explained in detail, it isto be understood that the invention is not limited to the details ofoperation or to the details of construction and the arrangement of thecomponents set forth in the following description or illustrated in thedrawings. The invention may be implemented in various other embodimentsand is capable of being practiced or being carried out in alternativeways not expressly disclosed herein. Also, it is to be understood thatthe phraseology and terminology used herein are for the purpose ofdescription and should not be regarded as limiting. The use of“including” and “comprising” and variations thereof is meant toencompass the items listed thereafter and equivalents thereof as well asadditional items and equivalents thereof. Further, enumeration may beused in the description of various embodiments. Unless otherwiseexpressly stated, the use of enumeration should not be construed aslimiting the invention to any specific order or number of components.Nor should the use of enumeration be construed as excluding from thescope of the invention any additional steps or components that might becombined with or into the enumerated steps or components. Any referenceto claim elements as “at least one of X, Y and Z” is meant to includeany one of X, Y or Z individually, and any combination of X, Y and Z,for example, X, Y, Z; X, Y; X, Z; and Y, Z.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a conventional forged wrench inaccordance with the prior art.

FIG. 2 is a perspective view of a conventional bar stock used to forge awrench in accordance with the prior art.

FIG. 3 is a perspective view of an angle wrench manufactured inaccordance with an embodiment of the present invention.

FIG. 4 is a perspective view of a flat stock suitable for use inconnection with the present invention.

FIG. 5 is a perspective view of a wrench blank laser cut from the flatstock.

FIG. 6 is a wireframe perspective of the wrench after three-dimensionalmachining of the handle.

FIG. 7 is an enlarged perspective view of the jaw portion of the wrench.

FIG. 8 is an enlarged perspective view of the jaw of the presentinvention compared to the jaw of a conventional forged wrench.

FIG. 9 is a top plan view of one jaw containing a hex head bolt.

DESCRIPTION OF THE CURRENT EMBODIMENT

Overview

The present invention is directed to a method for manufacturing handtools. In the illustrated embodiment, the method includes the generalsteps of providing a flat stock 100, such as sheet or plate stock,having a thickness that is at least equal to the maximum thickness ofthe tool; laser cutting the sheet or plate stock 100 to form a toolblank 12 by cutting the general two-dimensional shape of the tool; andthree-dimensionally shaping the tool blank 12 into a three-dimensionalworkpiece 10 using one or more machining operations that give the toolblank the desired three-dimensional shape. After laser-cutting, themethod may include supplemental sanding and/or grinding steps thatremove any irregularities resulting from the laser cutting process andhelp to provide the tool blank 12 or three-dimensional workpiece 10 withdesired final shape and surface quality. The method may also include thestep of heat treating the tool blank 12 or three-dimensional workpiece10 to provide the desired material properties. In the illustratedembodiment, the method includes a quench and tempering process.Additionally, the method may include the step of applying a surfaceprotection to the three-dimensional workpiece 10. In the illustratedembodiment, the step of applying a surface protection may include thestep of electroplating, applying black oxide coating, galvanizing orapplying a zinc phosphate coating.

The present invention is well-suited for use in manufacturing a widerange of hand tools, but is particularly well-suited for use inmanufacturing wrenches and even more particularly angle wrenches (orangle-head wrenches), and, in that context, provides significantadvantages over the conventional forging processes that have long beenused to manufacture wrenches. For the purposes of disclosure, thepresent invention is described in the context of an angle wrench (orangle-head wrench). It should be understood, however, that the presentinvention is not limited to the manufacture of wrenches, except to theextent expressly set forth, and may instead be readily adapted for usein manufacturing other hand tools.

Directional terms, such as “vertical,” “horizontal,” “top,” “bottom,”“upper,” “lower,” “inner,” “inwardly,” “outer” and “outwardly,” are usedto assist in describing the invention based on the orientation of theembodiments shown in the illustrations. The use of directional termsshould not be interpreted to limit the invention to any specificorientation(s). Further, in one aspect, the present invention isdescribed in the context of a series of method steps. It should be notedthat the order in which the steps are performed may vary fromapplication to application, and that the present invention should not belimited to implementation of the method steps in a specific order unlessto the extent expressly and unambiguously set forth in the claims.

Manufacturing Process

As noted above, the present invention is directed to the manufacture ofhand tools, including without limitation to a wide range of hand toolsthat have conventionally been manufactured using forging techniques andapparatus. It has been determined that, despite long-held belief, amanufacturing process involving laser cutting and three-dimensionalmachining can provide hand tools that are at least as strong and durableas hand tools manufactured through forging. For purposes of disclosure,the present invention will be described in connection with themanufacture of an angle-head wrench, such as angle-head wrench of FIG.3, but as noted above, may be used to manufacture a wide range of handtools.

The present invention may be used to manufacture hand tools from a widerange of materials depending on the desired material properties of thefinished hand tool. In the illustrated embodiment, the wrench 10 may bemanufactured from steel plate in the form of flat stock, such as sheetstock or plate stock 100 (See FIG. 4). The sheet or plate stock 100 inthis embodiment has a thickness that is essentially equal to the desiredmaximum thickness of the finished hand tool. With respect to theillustrated wrench 10, the sheet or plate stock has a thickness that isequal to the desired thickness of the wrench jaws 16 and 18. Thiseliminates the need to remove material from the sheet or plate stock atits thickest point(s), and therefore provides enhanced efficiency inmaterial usage and reduced machining operations.

In this embodiment, the steel first exists in a block which is muchthicker than its final thickness. The steel is heated above itsrecrystallization temperature, above 900° C., then rolled sequentiallythinner and thinner. Once it reaches its final dimensions, it cools toambient temperature. During the process, the high temperature surfaceoxidizes and creates a layer of scale, which in this embodiment isremoved. The flat stock is then annealed in order to soften it formachining.

The repetitive compressive forces from the rolling process will help toremove voids and pores from the steel that could have formed when themetal was poured. Similar to forging, this will result in a tougher,more consistent part than alternative forming methods, which can leavevoids or pores (such as casting or powder metal).

The hot rolling process causes the body centered cubic crystal structureof the iron to statistically favor a certain orientation within the flatstock. Because the crystals themselves are more/less stiff in certaindirections, the resulting flat stock is stiffer in its length and widthdirections and less stiff in its thickness direction. The highlyelongated grain structure that results from rolling gives higherstrength and ductility in the elongated direction at the cost of lowerstrength and ductility in perpendicular directions. In addition, stressand heat from the rolling process reduces grain size which increasesstrength of the material. This all is beneficial because most loading ofthe wrench will create stresses in the length and width directions.

The method and manner of providing the flat stock 100 may vary fromapplication to application. For example, the flat stock couldalternatively be cold rolled, however this process will be moreexpensive due to increased energy and processing required to roll thesteel at lower, more controlled temperatures.

Although the material properties of the flat stock may vary, the type ofsteel used should meet or exceed the hardenability, machinability,strength, and ductility parameters suitable for the hand tool beingmanufactured. In some applications involving the manufacture of wrenchesthat have comparable strength to a forged wrench, the materialproperties of the flat stock may meet or exceed the followingparameters:

-   -   a. Hardenability—The hardenability range of the steel is        relevant to allowing the metal to be soft and machinable during        manufacturing but very hard and strong once finished. The        material should, in some applications, be able to reach hardness        values of 25 HRC or less when annealed, and 40 or higher when        quenched and tempered. The lower end of the hardness range        permits machining by mill with less chatter, heat, and tool        wear. It also allows the part to much more easily be finished by        polishing, buffing, and/or abrasive media. The high hardness        correlates to a high tensile strength, but also allows the part        to transfer high torque loads without permanently deforming at        its contact surfaces.    -   b. Machinability—The steel may have a machinability of at least        40-50% relative to AISI 1112 carbon steel. This is helpful in        that the part can be effectively milled, in terms of speed, cut        quality, and tool wear. A low steel machinability will reduce        speed and cut quality while increasing tool wear. Although a low        steel machinability part can still be formed by this process,        the cutting will become less economical and effective.    -   c. Toughness—The material may have a high toughness, combining        yield and tensile strength with ductility as described in the        following paragraphs:        -   i. Strength—The steel may attain a yield strength of at            least 1000 MPa and a Tensile strength of 1100 MPa after heat            treatment and when the part is in its finished state. This            is beneficial when the part is transferring high torques and            therefore has high internal stresses.        -   ii. Ductility—The part should, in some applications, bend            before fracturing during use. Therefore, it may have an            elongation at break of at least 10%.

In order to improve the speed and quality of laser cutting and hand andvibration polishing processes, the steel may (but does not have to)undergo a pickle then oil process. The pickle process consists of aseries of cleaning and acid baths which remove the oxidation scale fromthe steel. It then passes through an oil bath in order to preserve thecleaned surface from further oxidation. The oil bath provides the steelwith a coating of oil that helps to prevent rust. While this may beachieved with a variety of different oils, it may also involvealternative substances that can help to protect against rust. Forexample, the process may use long lasting oils or other substances thatlast only a few days and can be rinsed easily with water. The pickle andoil is an optional step. If the steel is cold rolled, the benefits ofpickle and oil are significantly reduced because the cold rollingprocess does not produce as much surface scale as the hot rollingprocess and begins much cleaner.

The part is then “blank” cut to its general 2D shape using a laser withsufficient power, likely at least 3 kW power for a typical wrench. FIG.4 shows a flat stock 100 after the 2D blank 12 has been cut from theflat stock 100. An oxygen, nitrogen, oxygen-nitrogen combination, orambient air assist gas is beneficial to create an exothermic reaction,releasing energy to aid the laser cut. In one embodiment, the lasercutting step is implemented using a fiber laser, but similar results maybe achievable with other laser technology. The Mitsubishi ML3015eX-Ffiber laser is well-suited for use in manufacture of the illustratedwrench 10. In the illustrated embodiment, the wrench 10 is an angle-headwrench. In the illustrated embodiment, the 2D shape is cut with thelaser beam extending substantially perpendicularly to the plane of theflat stock 100, but the orientation of the laser beam with respect tothe flat stock 100 may vary from application to application. As shown inFIG. 5, the illustrated wrench blank 12 is formed with an elongatedhandle 14 having a first jaw 16 extending from one end of the handle 14and a second jaw 18 extending from the opposite end of the handle 14.The configuration of the handle 14 may vary from application toapplication. For example, the length and/or cross-sectional shape of thehandle 14 may be varied to tailor the wrench 10 for the desiredapplication. As shown, the illustrated wrench 10 is an open-end wrenchwith angled jaws 16 and 18. More specifically, the first jaw 16 is setat an angle of 30 degrees to the longitudinal extent of the handle 14and the second jaw 18 is set at an angle of 60 degrees. Further, in theillustrated embodiment, wrench jaws 16, 18 are laterally offset (orshifted) relative to the length of the handle 14. More specifically, thecenterline of each wrench jaw 16, 18 is significantly offset from thelongitudinal centerline of the handle 14. As noted above, the offsetrelationship between the handle 14 and the wrench jaws 16, 18 may makeit easier to use the wrench 10 with nuts and bolts situated in tightconfines. In the illustrated embodiment, the wrench jaws 16, 18 aremaximally offset or fully offset from the handle 14. For example, eachwrench jaw 16, 18 may be offset such that the curved outermost edge ofthe beam 20 is substantially aligned or substantially flush with thecorresponding linear edge of the handle 14. As perhaps best shown inFIG. 3, the wrench jaws 16, 18 and the handle 14 may be laterally offsetwith the longitudinal edge 15 of the handle 14 being essentially tangentto the curved-outermost edge 21 of the beam 20. In order to account fordifferent wrench sizes, the offset can be quantified relative to thenominal jaw opening (or hex) size. For typical wrenches manufacturedusing the process of the present invention, the offset is about 0.835times the nominal opening size. However, meaningful benefits may beobtained in alternative embodiments in which the offset is at least 0.75times the nominal opening size. For example, in a typical 10 mm wrenchin accordance with the present invention, the center point of the jawopening is offset from the centerline of the handle 14 by approximately8.35 mm. Experience has revealed that it is difficult or costprohibitive to form a jaw that is both shifted away from the body tomaximize access and at an appropriately large angle to form an optimalangle head wrench from a conventional bar stock using conventionalforging techniques and apparatus. As a result, the present inventionmakes it possible, from a practical standpoint, to provide wrenches witha wider range of jaw orientations. This would also be true for otherhand tools where the ability to produce complex shapes is limited by thepractical limitations of forging. Providing the wrench 10 with jaws setat different angular offsets facilitates use of the wrench in a widerrange of applications. The angular offsets of the first and second jaws16 and 18 in the illustrated embodiment are merely exemplary and mayvary from application to application. If desired, the jaws 16 and 18 maybe set at different angles in alternative embodiments. In onealternative embodiment, the first jaw 16 may, for example, be angled (asin the illustrated embodiment) and the second jaw 18 may be straight(i.e. aligned with the longitudinal extent of the handle). In anotheralternative embodiment, the first jaw 16 and the second jaw 18 may beset at the same angular offset, but have different jaw widths. Forexample, the first jaw 16 may be a 10 mm jaw and the second jaw 18 maybe an 11 mm jaw. In yet another alternative embodiment, the wrench maybe a combination wrench in which the first jaw is an open-end jaw (as inthe illustrated embodiment) and the second jaw is a box-end jaw. As canbe seen, the present invention may be used to manufacture wrenches ofessentially any type or style.

The 2D blank 12 is shaped to provide a three-dimensional workpiece 10having the desired final three-dimensional shape. In the illustratedembodiment, the machining process includes the step or steps of removingmaterial from the handle 14 portion of the blank 12 to bring the handle14 to the desired three-dimensional shape. For example, as shown in thewireframe illustration of FIG. 6, the handle 14 may be thinned (Seewireframe A1) and the longitudinal corners of the handle may be machinedto round the generally square corners (See wireframe A2) resulting fromthe laser cutting process. The thinning and rounding operations give thehandle 14 a somewhat oval cross section shape. In the illustratedembodiment, the handle 14 may be machined along its length to correspondin shape with a conventional forged wrench, but the size, shape andconfiguration of the three-dimensional handle may vary from applicationto application. Thinning the handle 14 may be desirable in someapplications to optimize material usage for size/weight/feel andfunctional strength. The jaw area may receive higher stress andtherefore benefit from greater thickness, while reducing the thicknessof the handle may provide the wrench with weight benefits. Whilemanufacture of the illustrated wrench 10 includes three-dimensionallyshaping the handle 14, this is merely exemplary and the machiningoperations may be used to give essentially any desired three-dimensionalshape to any and all portions of the hand tool.

In the illustrated embodiment, the two-dimensional blank 12 is machinedinto a three-dimensional workpiece 10 having the desiredthree-dimensional shape using a CNC mill or other cutting machines. Inthe context of a CNC mill, the mill could be 3, 4, or 5 axis, verticalor horizontal. For example, the Haas VF 3 axis CNC Mill is well-suitedfor use in manufacturing the illustrated wrench. Using a CNC mill allowsthe formation of shapes that could be difficult or impossible to achievein a forge, like tight radii or lateral curves. The optimal type of CNCfor the process is determined largely by the volume, geometry, and priceof the part. Although three-dimensionally machined using a CNC mill inthis embodiment, hand tools may alternatively be three-dimensionallymachined using other types of cutting machines.

The 3D workpiece 10 can, but may not necessarily, be marked or brandedwhile in the CNC machine by using the mill tool to engrave artworkdesigns. For example, the CNC machine may be used to label the size 26of the wrench and/or to add a brand name 24 or other similar markings tothe tool. If not marked at this stage, the wrench 10 can be separatelymarked in a variety of ways (stamping, etc.).

Although not shown in the illustrated embodiment, the workpiece can, inalternative embodiments, undergo a bending process as desired. Forexample, the workpiece can be bent during the manufacturing process toprovide a jaw that extends at an angle out of the plane of the handle.Although it is possible to apply the bend at different stages ofmanufacture, the bending step may typically occur after laser cuttingand either before or after three-dimensional machining. With wrenchesthat have jaws at opposite ends, the jaws may be bent out of the planeof the handle in opposite directions. The angle at which the jaw(s) isbent may vary from application to application as desired. In typicalapplications, this angle may be between 5 and 30 degrees.

In the illustrated embodiment, the three-dimensional workpiece 10 nextundergoes any desired surface treatment steps. For example, the surfacesof the workpiece 10 may be deburred/finished using conventionalfinishing methods such as, but not limited to, polishing, buffing,vibration polishing, electropolishing, shot blasting or shot peening.

Once the workpiece 10 is in its final shape and surface finish, it maybe heat treated. In this embodiment, the workpiece 10 is heat treated bya quench and temper process. The part is heated to above its eutecticpoint at ˜730° C. to about ˜850° C. It is then quickly cooled using anoil quench. Alternatively, a water quench could be used. The part isthen reheated below its eutectic point to about 450° C. to achievedesirable hardness. The tempering temperature could range from about300° C. to 550° C. while still achieving desirable material properties.The described heat treatment is merely exemplary and alternative heattreatment processes may be employed. For example, the 3D workpiece 10could alternatively be hardened using an austempering heat treatprocess. As another example, the 2D blank 12 and/or the 3D workpiece 10could be heat treated before machining and/or surface finishing,although this could be more difficult and expensive.

The 3D workpiece 10 then may be protected from corrosion by conventionalprotection methods such as, but not limited to, electroplating, blackoxide, galvanizing or zinc phosphate. The corrosion protection may beapplied using essentially any conventional techniques and apparatus.

In another aspect, the present invention provides improved wrenchgeometry that is optimized for strength and material usage. In order todesign a strong wrench 10, the present invention provides an equationfor the geometry of the wrench jaws, and more particularly for theheight of the beams 20 of each jaw 16 and 18. The equation is derivedfrom an understanding of how strength is evaluated and how to simplymodel the scenario of a wrench turning a bolt. As described in moredetail below, the equation provides the geometry of the wrench jawopening in order to optimize torque strength with material usage andspace. The final equation for the wrench geometry is shown in Equation 5below. To derive the equation, the wrench jaw was treated as acantilever beam fixed at one end and loaded normal to its length at theother end. As shown in FIG. 7, the jaw 16 includes a pair ofspaced-apart beams 20. In this embodiment, the beams 20 are symmetrical,and the equation provides the height, h, of each beam 20. Stressthroughout the beam 20 can be approximated by Equation 1 below where σis internal stress (MPa), M is moment (N*m), y is distance from neutralaxis (mm), and I is the beam cross section's second moment of area(mm⁴). Equation 1 is the equation from which all successive equationswere derived.

$\begin{matrix}{\sigma = \frac{My}{I}} & \left( {{Eq}.\mspace{14mu} 1} \right)\end{matrix}$

This simple equation can be expanded to represent an ideal geometry forthe wrench jaw “beam” through an h(x) equation, where h is height fromthe jaw opening plane (beam height) at x, the distance along the jawopening plane (beam length), measuring from the tip where force isapplied. Moment (M) is the cross product of force applied at the jaw (F)and the distance from the force application (x). Distance from neutralaxis can be substituted for h/2 assuming the neutral axis is halfwaybetween the jaw opening plane and height from the jaw opening. For arectangular beam cross section, I=(1/12)*th³, where t is the thicknessof the wrench jaw. Substituting and simplifying all of this is shownbelow in Equation 2, a modified version of Equation 1.

$\begin{matrix}{\sigma = {\frac{My}{I} = {\frac{Fx{h/2}}{{1/1}2th^{3}} = \frac{6Fx}{th^{2}}}}} & \left( {{Eq}.\mspace{14mu} 2} \right)\end{matrix}$

Rearranging Equation 2 gives the geometry of the wrench jaw, h(x), inEquation 3 below.

$\begin{matrix}{{h(x)} = \sqrt{\frac{6F}{t\;\sigma}x}} & \left( {{Eq}.\mspace{14mu} 3} \right)\end{matrix}$

This geometric equation is then determined by the force, F, wrenchthickness, t, and allowable stress, σ. For example, if the wrench jawbeam must withstand a 9,000 N force based on a 200 N*m torque spec, thejaw is 6 mm thick, and can reach 1,200 MPa before yielding, thisequation will generate the slimmest profile, shown in Equation 4 below.

$\begin{matrix}{{h(x)} = {\sqrt{\frac{6*900{0\lbrack N\rbrack}}{{{6\left\lbrack {mm} \right\rbrack}*1},{200\left\lbrack {MPa} \right\rbrack}}x} = \sqrt{{7.{5\left\lbrack {mm} \right\rbrack}}x}}} & \left( {{Eq}.\mspace{14mu} 4.} \right)\end{matrix}$

Every cross section throughout the jaw beam will reach the specifiedmaximum stress, meaning that there is no excess material or“over-designed” regions of the jaw. This geometry is shown in thediagram below. The equation can be applied to optimize material usageand maintain strength on nearly any open end wrench jaw that is used toturn fasteners. When solved for a specific wrench, the equation can besimplified with a constant, C₁, representing the F, t, and σ as inEquation 5 below. In one embodiment including 6 mm, 19 mm and 38 mmwrenches, specific constants were calculated using the variables F, t,and σ. It should be noted that the computed constants were modifiedslightly for use, in order to scale proportionally for all wrench sizes.For this application, a stress, σ, of 1,200 MPa was used in determiningthe constant for all three wrench sizes. The thickness, t, for thesmallest wrench size was predetermined and increased linearly withwrench size based on fastener/fitting contact area and accessibility.For each wrench size, the force at the jaw, F, was calculated based onthe forces resulting from loading the wrench to ANSI proof torque. Forthe smallest (6 mm) wrench, F=1,136 N, t=4.35 mm, giving constant C1 of1.31 mm. The constant was adjusted to 1.69 for this size. For a medium(19 mm) wrench, F=9,022 N, t=7.34 mm, giving constant C1 of 6.14 mm. Theconstant was adjusted to 5.34 for this size. Finally, for the larger (38mm) wrench, F=23,440 N, t=11.71 mm, giving constant C1 of 10.01 mm. Theconstant for the larger wrench was adjusted to 10.69. So, for thisexemplary set of wrenches, each unique angle wrench size may have adifferent constant, C₁, ranging from 1.69 mm to 10.69 mm. For mostcommon wrench applications, C₁ will fall between 0.5 mm and 50 mm.

$\begin{matrix}{{h(x)} = {\sqrt{\frac{6F}{t\;\sigma}x} = \ \sqrt{C_{1}x}}} & \left( {{Eq}.\mspace{14mu} 5} \right)\end{matrix}$

In addition to providing an optimized jaw geometry, the presentinvention also allows for the manufacture of wrenches with optimized jawopening 30 geometry. In this embodiment, the radii in the corners 22 ofthe jaw opening 30 are designed larger than conventional wrenches. Sharpcorners create stress concentrations with higher stresses at the cornerthan at other parts of the cross section. Larger radii at corners willreduce the stress in the given corner. In the case of wrenches, such aswrench 10, a larger radius in the jaw corner 22 will result in lowerinternal stress at the corner 22 for a given torque.

In the illustrated embodiment, the radii of the corners 22 in the firstand second jaws 16 and 18 are as large as possible in order to reduceinternal stresses and increase strength. In this embodiment, thesize/radii of the corners 22 is constrained by hex contact. For example,as shown in FIG. 9, the flat portions 28 of the jaw are at least of thesame length as the flat sections of the bolt head B. If the radius istoo large, the flat portion 28 of the wrench opening will decrease suchthat the hexagonal fastener will no longer adequately contact the flats28 of the jaw opening 30.

For these angle wrenches, the radius size, R, is about ⅓ the size of thejaw opening size, d, as in Equation 6 below, where C₂ is a dimensionlessconstant. For this application, C₂ could range from about 2.5 to 3.8while maintaining strength benefits of a large radius and still fittinga hexagonal fastener properly.

$\begin{matrix}{R = {\frac{d}{C_{2}} = \frac{d}{3.1}}} & \left( {{Eq}.\mspace{14mu} 6} \right)\end{matrix}$

To illustrate, FIG. 8 compares a jaw 16 manufactured in accordance withthe present invention to a combination wrench 200 that is commerciallyavailable from a well-known manufacturer/supplier of hand tools. As canbe seen, the angle wrench 10 of the present invention has significantlylarger radius corners 22 than the radius corners 222 of the commerciallyavailable wrench 200.

The laser cutting and machining process for wrench manufacture has someinherent advantages over forging in its ability to form complex ornon-linear geometries. For the case of wrenches and other hand tools,the metal generally starts as a straight, cylindrical billet (See FIGS.1 and 2). Shapes created in a forging process are limited to how far themold can stretch or smash the metal. For example, the capital letter “T”would be very difficult to forge because it would require the straightbillet to be stretched dramatically in at least one directionperpendicular from its axis. When laser cut from a plate of steel,however, a capital “T” would be very simple to form. This difference isrelevant to wrenches with forms that deviate from a straight handleaxis. For example, these angle wrenches have large angular andlocational jaw offsets relative to the handle when compared to othercommon wrenches (such as combination wrenches). This shape would requirethe steel billet material to stretch more. This increased stretch couldrequire higher forge temperatures, higher press forces, or multi-stagemolds. These in turn could increase tool wear or even make the geometryimpossible to reasonably form. On a laser machine, however, essentiallyany two-dimensional shape can be cut, without the laser thinking twice.

There are, however, options to bend the steel before or after forging.For example, if you were to forge an “S” shape, you could first bend thebillet in two locations to form a backward “Z” shape. The “Z” billetwould then be forged to form an “S”. This process increases theversatility of forging, but still does not easily permit shapes like “T”to be formed.

The above description is that of current embodiments of the invention.Various alterations and changes can be made without departing from thespirit and broader aspects of the invention as defined in the appendedclaims, which are to be interpreted in accordance with the principles ofpatent law including the doctrine of equivalents. This disclosure ispresented for illustrative purposes and should not be interpreted as anexhaustive description of all embodiments of the invention or to limitthe scope of the claims to the specific elements illustrated ordescribed in connection with these embodiments. For example, and withoutlimitation, any individual element(s) of the described invention may bereplaced by alternative elements that provide substantially similarfunctionality or otherwise provide adequate operation. This includes,for example, presently known alternative elements, such as those thatmight be currently known to one skilled in the art, and alternativeelements that may be developed in the future, such as those that oneskilled in the art might, upon development, recognize as an alternative.Further, the disclosed embodiments include a plurality of features thatare described in concert and that might cooperatively provide acollection of benefits. The present invention is not limited to onlythose embodiments that include all of these features or that provide allof the stated benefits, except to the extent otherwise expressly setforth in the issued claims. Any reference to claim elements in thesingular, for example, using the articles “a,” “an,” “the” or “said,” isnot to be construed as limiting the element to the singular.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A method ofmanufacturing a wrench having a handle and at least one jaw, comprisingthe steps of: providing a flat stock, the flat stock having a thicknessequal to a maximum thickness of the at least one jaw; laser-cutting theflat stock to form a wrench blank, the wrench blank forming anunfinished handle portion and an unfinished jaw portion, the unfinishedjaw portion extending from the unfinished handle portion, the unfinishedhandle portion and the unfinished jaw portion of the wrench blank havinga uniform thickness equal to the thickness of the flat stock;three-dimensionally machining the unfinished handle portion of thewrench blank to cut material from and reduce the maximum thickness ofthe unfinished handle portion of the wrench blank without reducing themaximum thickness of the unfinished jaw portion, thereby providing athree-dimensional workpiece with the unfinished handle portion havingthe desired three-dimensional shape and wherein the unfinished handleportion has a maximum thickness less than the maximum thickness of theunfinished jaw portion; finishing the three-dimensional workpiece; andheat treating the three-dimensional workpiece to arrive at the wrench,the at least one wrench jaw having a maximum thickness equal to thethickness of the flat stock and the wrench handle having a maximumthickness lesser than the thickness of the at least one wrench jaw. 2.The method of claim 1 wherein the at least one jaw includes a pair ofspaced apart beams, each of the beams having a geometry with a height,h, in accordance with following the equation:${h(x)} = \sqrt{\frac{6F}{t\sigma}x}$ where F is a predetermined force,t is a thickness of the beam and σ is an allowable stress.
 3. The methodof claim 1 wherein the wrench is an angle wrench having at least one jawand a handle, the at least one jaw being oriented at an angle to alongitudinal extent of the handle.
 4. The method of claim 3 wherein theangle is at least 7.5 degrees.
 5. The method of claim 1 wherein the atleast one jaw includes a pair of beams spaced apart to define a wrenchopening with a size, each of the beams having a flat hex engagementsurface, each of the flat hex engagement surfaces joined to theremainder of the wrench at a separate internal corner, each internalcorner having a radius of about one-third of the size of the wrenchopening.
 6. The method of claim 1 wherein the wrench jaw includes a pairof beams spaced apart to define a wrench opening with a size, each ofthe beams having a flat hex engagement surface, each of the flat hexengagement surfaces joined to the remainder of the wrench at a separateinternal corner, each internal corner having a radius equal to the sizeof the wrench opening divided by C, where C is in the range of about 2.5to 3.8.
 7. The method of claim 1 wherein the laser-cutting step includesforming the at least one jaw portion at an offset from a longitudinalcenter of the handle, wherein the jaw portion includes a beam having acurved outer edge and the handle portion includes a linear longitudinaledge; and wherein the offset is selected such that the longitudinal edgeof the handle portion is substantially tangent to the outer edge of thebeam.
 8. The method of claim 1 further including the step of bending atleast one of the wrench blank or the three-dimensional workpiece tocreate an angle between the jaw and the handle of the wrench.
 9. Themethod of claim 1 wherein the three-dimensional machining step includesthree-dimensionally machining an interface region between the wrenchhandle and the wrench jaw.
 10. A method of manufacturing a wrench,comprising the steps of: providing a flat stock, the flat stock having athickness equal to a maximum thickness of the wrench; laser-cuttingthrough the thickness of the flat stock to form the two-dimensionalwrench blank having a wrench handle and at least one wrench jawextending from the handle, the wrench blank being of uniform thicknessequal to the thickness of the flat stock; three-dimensionally machiningat least a portion of the wrench handle to cut material from the maximumthickness of the wrench handle without cutting material from the maximumthickness of the at least one wrench jaw to provide a three-dimensionalworkpiece, the wrench handle of the three-dimensional workpiece having athree-dimensional shape and a maximum thickness less than the thicknessof the flat stock and the maximum thickness of the at least one wrenchjaw, the wrench jaw of the three-dimensional workpiece having a maximumthickness equal to the thickness of the flat stock; and finishing thethree-dimensional workpiece, the wrench handle of the finishedthree-dimensional workpiece having a maximum thickness less than amaximum thickness of the wrench jaw of the finished three-dimensionalworkpiece.
 11. The method of claim 10 wherein said machining step isfurther defined as cutting material from a full length of the wrenchhandle to provide at least a portion of the wrench handle with athree-dimensional shape without removing material from the thickness ofthe wrench jaw.
 12. The method of claim 11 wherein the wrench jawincludes a pair of spaced apart beams, each of the beams having ageometry with a height, h, in accordance with following the equation:${h(x)} = \sqrt{\frac{6F}{t\sigma}x}$ where F is a predetermined force,t is a thickness of the beam and σ is an allowable stress.
 13. Themethod of claim 10 wherein the at least one wrench jaw includes a pairof beams spaced apart to define a wrench opening with a size, each ofthe beams having a flat hex engagement surface, each of the flat hexengagement surfaces joined to the remainder of the wrench at a separatecorner, each internal corner having a radius equal to the size of thewrench opening divided by C, where C is in the range of about 2.5 to3.8.
 14. The method of claim 10 wherein the wrench is an angle wrenchhaving the wrench jaw oriented at an angle of at least 7.5 degrees to alongitudinal extent of the wrench handle.
 15. The method of claim 10wherein the three-dimensional machining step includesthree-dimensionally machining an interface region between the wrenchhandle and the wrench jaw.
 16. An angle-head wrench comprising: a wrenchbody having a handle and at least one jaw extending from the handle, thejaw extending at an angle to the longitudinal extent of the handle, thewrench body being laser cut from a flat stock having a thickness equalto a thickness of the jaw, the handle having at least one portion with athree-dimensional shape, the three-dimensional portion shaped from atleast one machining operation cutting material from the thickness of theflat stock to reduce the maximum thickness of the handle lower than themaximum thickness of the jaw.
 17. The angle-head wrench of claim 16wherein the jaw includes a pair of spaced apart beams, each of the beamshaving a geometry with a height, h, in accordance with following theequation: ${h(x)} = \sqrt{\frac{6F}{t\sigma}x}$ where F is apredetermined force, t is a thickness of the beam and σ is an allowablestress.
 18. The angle-head wrench of claim 16 wherein the jaw includes apair of beams each having a flat hex engagement surface, each of theflat hex engagement surfaces joined to the remainder of the wrench alonga radius, the radius being maximized such that each flat hex engagementsurface is at least approximately equal in length to a length of asurface of a hex head fastener of corresponding size.
 19. The angle-headwrench of claim 16 wherein the jaw is oriented at an angle of at least7.5 degrees to a longitudinal extent of the handle.
 20. The angle-headwrench of claim 16 wherein the jaw includes a beam having a curved outeredge and the handle includes a linear longitudinal edge; and wherein thejaw is offset from the longitudinal center of the handle with thelongitudinal edge of the handle being substantially tangent to the outeredge of the beam.